1. Field of the Invention
This invention relates to an internal combustion engine mounted on a personal watercraft for operation in water. More particularly, the invention relates to an internal combustion engine having an improved oil pan structure.
2. Description of the Background Art
The personal watercraft, or small-sized planing boat, is constructed such that an internal combustion engine for driving a jet propulsion pump is mounted in a vessel body enclosed by a hull and a deck. A driver and up to two other crew members rides on the deck, so that an in-boat space, constituted by the hull and the deck, is narrow. The internal combustion engine is stored in a substantially closed and sealed state within the narrow space between the hull and the deck.
As a consequence, a compact internal combustion engine is required. In order to minimize the height of the internal combustion engine, a dry sump having no oil reservoir for accumulating a large amount of oil is employed. Such an internal combustion engine is disclosed, for example, in published Japanese patent document JP-A 2003-35201.
The oil pan in JP-A No. 2003-35201 is not used for accumulating a large amount of oil. However, a small amount of oil is accumulated in a certain receiving pan, and the accumulated oil is sucked by an oil pump and fed to an oil tank. An oil strainer is arranged within the oil pan in tension, and is oriented substantially horizontally therein. The accumulated oil is sucked through the oil strainer whereby some foreign substances are removed from the oil.
Since the oil strainer is arranged in tension within the oil pan in a substantially horizontal orientation, a certain degree of lateral width of the oil pan is required. It is not easy to align the oil strainer in compliance with an oil pan shape, which is increasing rightward or leftward at the central part of the boat bottom of the personal watercraft. In addition, it is necessary to configure a space having a certain degree of vertical distance above and below the horizontally oriented oil strainer, and providing the required narrow vertical distance for the oil pan is difficult.
The present invention has been invented in view of the considerations described above, and it is an object of the present invention to provide an internal combustion engine for a personal watercraft in which the lateral width of the oil pan is narrow and its vertical width is also kept short, in compliance with a shape of the boat bottom part of the personal watercraft. As a result, the overall height of the internal combustion engine is kept short.